In general, image sensors are semiconductor devices for converting an optical image into an electrical signal. Among types of image sensors, a CMOS image sensor is a device employing a switching mode to sequentially detect an output by providing photodiodes corresponding to the number of pixels through a CMOS technology that uses peripheral devices, such as a control circuit and a signal processing circuit.
In manufacturing the image sensor various efforts have been made to improve the photosensitivity of the image sensor.
The CMOS image sensor is composed of a pixel array unit including photodiodes for sensing light and a CMOS logic circuit for processing the detected light into electrical signals, to convert them into data. In order to improve photosensitivity, either the area occupied by the photodiodes must be increased, or a photo-gathering technology must be used to collect more light in the photodiode area by focusing the light path and forming a micro-lens over the upper portion of the photodiodes.